Stacked III-V semiconductor photonic device

ABSTRACT

A stacked III-V semiconductor photonic device having a second metallic terminal contact layer at least formed in regions, a highly doped first semiconductor contact region of a first conductivity type, a very low doped absorption region of the first or second conductivity type having a layer thickness of 20 μm-2000 μm, a first metallic terminal contact layer, wherein the first semiconductor contact region extends into the absorption region in a trough shape, the second metallic terminal contact layer is integrally bonded to the first semiconductor contact region and the first metallic terminal contact layer is arranged below the absorption region. In addition, the stacked III-V semiconductor photonic device has a doped III-V semiconductor passivation layer of the first or second conductivity type, wherein the III-V semiconductor passivation layer is arranged at a first distance of at least 10 μm to the first semiconductor contact region.

This nonprovisional application claims priority under 35 U.S.C. § 119(a)to German Patent Application No. 10 2020 001 842.4, which was filed inGermany on Mar. 20, 2020 and which is herein incorporated by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a stacked III-V semiconductor photonicdevice.

Description of the Background Art

III-V semiconductor diodes are now used in a wide variety ofapplications, each with adapted parameters.

From “GaAs Power Devices” by German Ashkinazi, ISBN 965-7094-19-4, pp. 8and 9, a high-voltage-resistant semiconductor device made of GaAs withp+-n-n+ is known.

Further high-voltage III-V semiconductor devices and correspondingmanufacturing methods are also described in the publications DE 10 2016013 540 A1 (which corresponds to U.S. Pat. No. 10,263,124), DE 10 2016013 541 A1 (which corresponds to U.S. Pat. No. 10,074,540), DE 10 2016015 056 A1 (which corresponds to U.S. Pat. No. 10,192,745), DE 10 2017002 935 A1 (which corresponds to U.S. Pat. No. 10,312,381) and DE 102017 002 936 A1 (which corresponds to U.S. Pat. No. 10,340,394), andwhich are all herein incorporated by reference.

III-V semiconductor devices are also used as pixels or semiconductordetectors in 2D pixel array detectors.

For example, infrared detectors are known from “InGaAs NIR focal planearrays for imaging and DWDM applications”, Barton et al, InfraredDetectors and Focal Plane Arrays VII, Proc. of SPIE Vol. 4721, 2002.

The described III-V semiconductor diode structures each feature alattice-matched InGaAs absorption region on an n+ doped InP substrate, adiffusion-generated p+ contact region, and a III-V semiconductorpassivation layer. Corresponding infrared detectors are also known from“Multiplexed 256 Element InGaAs Detector Arrays for 0.8-1.7 umRoom-Temperature Operation”, Olsen et al., Infrared Technology XIV, SPIEVol. 972, 279 and from “InGaAs focal plane arrays developments atIII-VLab”, Rouvie et al., Infrared Technology and Applications XXXVIII,Proc. of SPIE Vol. 8358, 835308, 2012, doi: 10.1117/12.921134.

Also from “FPA Development from InGaAs InSb to HgCdTe”, Yuan et al,Infrared Technology and Applications XXXIV, Proc. of SPIE Vol. 6940,69403C, 2008, doi: 10.1117/12.782735, an infrared detector is known,wherein different p-i-n structures with InGaAs having different indiumcontent are described as an absorption region on an InP substrate,optionally with a buffer layer, as well as pixel arrays based on InSband HgCdTe.

From “A Method for Adjusting the Performance of Epitaxial GaAs X-rayDetectors”, Sun, G. C. and Bourgoin, J. C., Nucl. Instrum. Methods Phys.Res., Sect. A, 2003, vol. 512, pp. 355-360, from “GaAs Schottky versusp/i/n Diodes for Pixellated X-ray Detectors”, Bourgoin, J. C. and Sun,G. C., Nucl. Instrum. Methods Phys. Res., Sect. A, 2002, vol. 487, pp.47-49, also from DE 602 21 638 T2, a method and apparatus formanufacturing a GaAs detector for X-ray detection and image acquisitionis known. Furthermore, another GaAs image acquisition device for thedetection of X-rays is known from WO 2004 816 04 A2.

P-i-n structures made of a GaAs compound are known as pixels of an X-raydetector from “GaAs Pixel-Detector Technology for X-ray MedicalImaging”, Lezhneva et al, a Russian Microelectronics, Vol. 34, No. 4,2005, pp. 229-241, wherein both epitaxially grown and implanted p+contact regions are disclosed. Alternatively, GaAs-based Schottky diodesare disclosed.

A GaAs-based X-ray detector, also based on Schottky diodes, is knownfrom “GaAs X-Ray System Detectors for Medical Applications”, Rizzi etal, https://www.researchgate.net/publication/237780321.

A disadvantage of the described structures are the residual or leakagecurrents that occur during reverse-bias mode especially across the edgesof the planar p-n junctions or the mesa structures.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a devicewhich improves on the prior art. In particular, the aim is to reducereverse leakage currents and increase the breakdown voltage.

In an exemplary embodiment of the invention, a stacked III-Vsemiconductor photonic device is provided.

The stacked III-V semiconductor photonic device can have a secondmetallic terminal contact layer formed at least in regions, a highlydoped first semiconductor contact region, an absorption region, and afirst metallic terminal contact layer.

The first semiconductor contact region can be of a first conductivitytype with a dopant concentration of at least 5·10¹⁸ cm⁻³, a firstlattice constant and a first energy bandgap.

The absorption region is of a second conductivity type or of the firstconductivity type, wherein a dopant concentration in the absorptionregion is between 8·10¹¹ and 5·10¹⁴ cm⁻³. Preferably, the absorptionregion has a uniform dopant concentration. In another embodiment, thedopant concentration varies across the thickness of the absorptionregion.

The absorption region has the first lattice constant and a layerthickness in a range between 80 μm and 2000 μm, preferably from 100 μmto 2000 μm or from 500 μm to 2000 μm or from 1000 μm to 2000 μm.

The first semiconductor contact region can be trough-shaped with a topside and a depth extending into the absorption region. Preferably, thetop side of the first semiconductor contact region is completelysurrounded by a top side of the absorption region.

The bottom side of the second metallic terminal contact layer can beintegrally bonded to the top side of the first semiconductor contactregion.

The first metallic terminal contact layer can be arranged below a bottomside of the absorption region.

The stacked III-V semiconductor photonic device further comprises aIII-V semiconductor passivation layer having the first lattice constantand a second energy bandgap which differs from the first energy bandgap,wherein the III-V semiconductor passivation layer includes the first orthe second conductivity type and a dopant concentration in a rangebetween 1·10¹⁴ cm⁻³ and 5·10¹⁸ cm⁻³.

The III-V semiconductor passivation layer can be arranged at a firstdistance of at least 10 μm or of at least 20 μm or of at least 40 μmfrom the top side of the first semiconductor contact region on the topside of the absorption region and is integrally bonded to the top sideof the absorption region.

Preferably, the first distance is a maximum of 40 μm or a maximum of 80μm or a maximum of 150 μm or a maximum of 1500 μm or a maximum of 2000μm.

It should be noted that the metallic terminal contact layers each havevery good electrical conductivity. Preferably, the metallic terminalcontact layers are formed of one or more metal layers, wherein the metallayers preferably comprise Ge and/or Au and/or Pd and/or Ag.

The metallic terminal contact layers establish an electricallylow-impedance contact to the highly doped first semiconductor contactregion and to another doped semiconductor contact region, e.g. a highlydoped second semiconductor contact layer or the very low dopedabsorption region. It is understood that the respective semiconductorlayer is in each case directly connected to the corresponding metallicterminal contact layer, i.e. it is integrally bonded to it.

It is further understood that the terminal contact layers can beinterconnected by means of bonding wires with contact fingers, so-calledpins, and/or by means of contact points, so-called bumps, with flip-chipmounting, in that preferably multiple or a plurality of photonic devicesare arranged on a carrier, for example in the form of a lead frame. Inone embodiment, the photonic devices are arranged in a matrix.

The first semiconductor contact region can be formed as a regionextending into the absorption region, so that the top side of the firstsemiconductor contact region and the top side of the absorption regionform a common surface, or the top side of the first semiconductorcontact region is located in an island shape within the top side of theabsorption region.

However, it is understood that the first semiconductor contact region isalways spaced from the III-V semiconductor passivation layer by asurface formed by the absorption region. In other words, the III-Vsemiconductor passivation layer is always spaced from the edge of thefirst semiconductor contact region by at least 10 μm. The maximumdistance is as great as the thickness of the absorption region.

The first semiconductor contact region extends from the top side to amaximum depth into the absorption region, wherein the layer thickness ofthe absorption region is significantly greater than the depth of thefirst semiconductor contact region.

Preferably, at an edge of the III-V semiconductor passivation layerformed in the direction of the first semiconductor contact region, theotherwise planar surface of the absorption region can have acircumferential step formed along the edge.

The first semiconductor contact region can be preferably created byimplantation or diffusion. The other semiconductor regions orsemiconductor layers, e.g. the absorption region and/or the III-Vsemiconductor passivation layer, are preferably produced partially orcompletely epitaxially, e.g. by means of MOVPE or by means of CSVT(Closed Space Vapor Transport) or by means of LPE.

For example, a GaAs substrate or a Ge substrate is used as the growthsubstrate. In the case of the GaAs substrate, active layers of GaAs canbe deposited directly on the substrate. In the case of the Ge substrate,an InGaAs interlayer with an In content of approx. 1% is required forthe growth of GaAs layers, in order to achieve a lattice constantdifference between the Ge substrate and the GaAs epitaxial layer.

The growth substrate is then preferably completely, if necessary alsoonly partially, removed by grinding and/or etching and/or otherprocesses, e.g. detaching.

In an example, an etch stop layer is inserted below the absorptionregion for this purpose during a manufacturing process of the stackedIII-V semiconductor device. The etch stop layer is produced, forexample, between the absorption region and a buffer layer or a substratelayer, or between a second semiconductor contact layer and a bufferlayer or a substrate layer, or between a buffer layer and a substratelayer.

The etch stop layer allows for subsequent removal of the substrate layerand the buffer layer or of only the substrate layer by means of anetching process, e.g. wet chemical etching. In particular, the etch stoplayer enables the substrate and/or buffer layer to be removed without amechanical grinding process or to combine a mechanical grinding processwith an etching step, e.g. most of the substrate is removed by grindingand only the remaining part is removed by chemical etching.

The etch stop layer itself can also be removed afterwards. The etch stoplayer exhibits a strong chemical anisotropy as compared to the adjacentlayers, i.e. the etch rate for the etch stop layer and the adjacentlayer differ by at least a factor of 10.

The etch stop layer usually consists of or is formed of GaInP or AlGaAs,and the surrounding layers of GaAs or GaInAs. The removed layers are nolonger present in the final device.

The semiconductor layers of the device, for example made of GaAs, areproduced epitaxially. Later, for example, first the Ge-substrate isremoved by means of a grinding and/or etching process and, if necessary,a buffer layer is then removed from the GaAs photonic device by means ofa further etching process, e.g. wet chemical etching.

As an alternative to the complete removal of the growth substrate, thegrowth substrate, e.g. a GaAs substrate doped with the secondconductivity type, is only partially removed so that a remaining, e.g.thin to very thin, layer forms a highly doped second semiconductorcontact layer of the second conductivity type.

Alternatively or complementarily, one or more layers of the stackedIII-V semiconductor photonic device are bonded together by means of awafer bond.

It should also be noted that the term “semiconductor layer” can be usedsynonymously with the term “semiconductor region”. However, the term“semiconductor region” is used to refer to a generally trough-shapedformation of the intermediate region, and the term “semiconductor layer”commonly refers to a layer having at least a planar bottom side and/or aplanar top side.

Preferably, the III-V semiconductor layers are each at least partiallyplanar or partially trough-shaped with respect to one another, whereinthe lateral formation of the respective III-V semiconductor layers forthe planar arrangement is preferably the same size.

It is understood that only the semiconductor regions or semiconductorlayers or at least a major part of the semiconductor regions orsemiconductor layers of the III-V photonic device consist of or isformed of III-V materials, e.g. GaAs, AlGaAs, InGaP, GaAsP, InGaAs orInP. The III-V semiconductor photonic device may thus additionallycomprise semiconductor layers of other semiconductor materials, oradditional layers of other non-semiconductor materials.

Furthermore, it is understood that a semiconductor region orsemiconductor layer consisting of a III-V material must onlysubstantially consist of III-V material or, in addition to a III-Vmaterial, i.e. a material which contains one or more elements of themain groups III and/or V, may still contain contaminants, impuritiesand/or dopants.

The same applies to a semiconductor region, or a semi-conductor layer,made of GaAs or another expressly named material combination. If a layerhas an expressly named material combination, this means that thematerial of the layer essentially consists of a combination of theexpressly named materials and optionally other elements of main groupsIII and/or V. A layer comprising GaAs can thus, for example, be anInGaAs layer.

Low doped thick layers, such as the absorption layer according to theinvention, can now be deposited using MOVPE, for example, which makes iteasy to produce layer stacks. The lower the doping level of the layer,the lower the reverse voltage required to build up the largest possibleelectric field. As a follow up, the layers can also be irradiated byelectrons with e.g. 1 MeV in order to generate EL2 recombination centersuniformly over the entire layer thickness, which then lower the dopinglevel of the thick layer even further in a very defined way by trappingan electron or a hole.

It is also understood that the III-V semiconductor photonic device maybe formed with an n-on-p or a p-on-n structure. Correspondingly, eitherthe first conductivity type is n and the second conductivity type p, orvice versa.

If the semiconductor device does not have an additional secondsemiconductor contact layer, the conductivity type of the absorptionregion differs from the conductivity type of the first semiconductorcontact region, i.e. the absorption region is of the second conductivitytype and the p-n junction is formed between the first semiconductorcontact region and the absorption region.

If the semiconductor device has a second semiconductor contact layer,the p-n junction may be formed either between the absorption region andthe first semiconductor contact region or between the absorption regionand the second semiconductor contact layer, wherein the absorptionregion is of either the second or the first conductivity type,respectively.

If necessary, thanks to the local p-n junction between the firstsemiconductor contact region and the absorption layer and in particularthanks to the III-V semiconductor passivation layer, leakage currents inthe edge region or in the current path running over the edge aresuppressed.

Studies have shown that the breakdown voltage is not only determined bythe thickness of the absorption region but also significantly by thefirst distance between the III-V semiconductor passivation layer and thefirst semiconductor contact region.

With the photonic device according to the invention, breakdown fieldstrengths of up to 40 V/μm and very reliable breakdown field strengthsof up to 50 V/μm can be achieved.

III-V semiconductors, in particular GaAs, provide a particularly highelectron mobility of 8800 Vs/cm at a doping of less than 1·10¹⁵ cm³,wherein the electron mobility for InGaAs of about 12,000 Vs/cm is at adoping of less than 1·10¹⁵ cm⁻³.

Advantages of the semiconductor structure according to the invention area particularly low reverse leakage current and a high breakdown voltage.In particular, the breakdown characteristic exhibits an ideal curve.

With the particularly thick absorption region above 80 μm, up to athickness of 2000 μm or a thickness between 100 μm and 2000 μm, and theparticularly high reverse voltage, the semiconductor structure accordingto the invention is particularly suitable as a pixel for radiationdetection, in particular for the detection of X-rays. In other words,the photonic component is particularly suitable as an X-ray detector.

By providing a gap between the III-V semiconductor passivation layer andthe first semiconductor contact region, particularly low reverse leakagecurrents of less than 1 μA occur even at high reverse voltages above 400V. In particular, the reverse leakage currents are in a range between0.5 nA and 50 nA or below 100 nA.

This allows for high reverse voltages to be applied in order to driftthe charge carriers produced by the absorption in the direction of thep-n transition. It is understood that this allows for a very highsensitivity of the detector to be achieved.

The particularly thin first metallic connection layer is preferably notflat but finger-shaped or strip-shaped or dot-shaped. By means of a thinsecond semiconductor contact layer or by omitting the secondsemiconductor contact layer, the permeability for photons, for exampleX-rays, is increased. This allows for the semiconductor photonic deviceaccording to the invention to be used, in particular, as a pixel of apixel array X-ray detector. Preferably, the first metallic terminallayer has a thickness less than 100 μm and greater than 0.1 nm.

It is also understood that the photonic device can be aligned for thedetection of rays so that these impinge on the first metallic terminalcontact layer and the bottom side of the device. The terms “bottom” and“top” or “below” and “above” are used only to refer to the arrangementof the individual layers and regions relative to each other and do notgive an absolute direction.

In an example, the III-V semiconductor passivation layer has a layerthickness of 0.1 μm-10 μm. Preferably, the III-V semiconductorpassivation layer has a higher bandgap than the absorption region lyingbelow. In particular, the III-V semiconductor passivation layercomprises, for example, a compound of InGaP and/or AlGaAs and/orInGaAsP, or consists of AlGaAs or of InGaP or of InGaAsP. In anotherfurther development, further passivation layers, in particular formedfrom silicon nitride and/or silicon oxide, are also formed on the III-Vsemiconductor passivation layer.

In another example, the first distance of the III-V semiconductorpassivation layer to the first semiconductor contact region is at least50% or at least 75% of the layer thickness of the absorption region.

It is understood that the first distance depends on the reverse voltage.The greater the reverse voltage, the greater the first distance must be.This results in a corresponding relationship between the distance andthe layer thickness of the absorption region.

In another example, in a projection perpendicular to the top side of thefirst semiconductor contact region, the III-V semiconductor passivationlayer fully encloses the first semiconductor contact region.

Thus, the III-V semiconductor passivation layer has a through hole inthe projection, and the first semiconductor contact region is arrangedwithin the through hole such that a distance of an edge of the firstsemiconductor contact region to an edge of the through hole is alwaysgreater than, or equal to, the first distance.

In an example, the III-V semiconductor passivation layer is of the sameconductivity type as the absorption region. The III-V semiconductorpassivation layer and the absorption region are thus either bothp-doped, or both n-doped.

Alternatively, the III-V semiconductor passivation layer has a layerthat is separated from the absorption region, wherein the III-Vsemiconductor passivation layer is integrally bonded to a third metallicterminal contact layer formed at least in regions.

In particular, the absorption region is of the first conductivity typeand the III-V semiconductor passivation layer is of the secondconductivity type and the third metallic terminal contact layer isintegrally bonded to the top side of the III-V semiconductor passivationlayer.

In example, the III-V semiconductor passivation layer is epitaxiallyarranged on the absorption region and the absorption region isepitaxially arranged on a semiconductor contact layer or on a bufferlayer or on a substrate layer.

In another further development, the first metallic terminal contactlayer has a layer thickness of 5 nm-2 μm or 10 nm-1 μm. Since only verylow currents of less than half 1 mA, preferably less than 10 μA, flow inthe photonic component, thin metallic terminal contact layers aresufficient.

In an example, the first metallic connection contact layer is flat orfinger-shaped or dot-shaped.

The term “flat” can refer to a terminal contact layer that completelycovers, or at least covers to a large extent, e.g. 70%, the bottom sideof the lowermost semiconductor layer of the III-V semiconductor photonicdevice, e.g. the absorption region or the semiconductor contact layer.

A dot-shaped terminal contact layer, on the other hand, covers only asmall portion of the top side of the lowest semiconductor layer of thedevice, e.g. 20% or 10%. It is understood that the shape, e.g. thecircumference, of the dot-shaped terminal contact layer can bearbitrary, e.g. circular, oval or polygonal, for example square.

A finger-shaped terminal contact layer only partially covers the bottomside of the lowermost semiconductor layer with individual elongated,strip-shaped or dot-shaped terminal contact layer sections and, ifnecessary, with a connecting transverse or only local terminal contactlayer section, and is therefore the preferred embodiment for thesemiconductor photonic device.

In an example, the first semiconductor contact region and the absorptionregion and/or a second semiconductor contact layer of the III-Vsemiconductor photonic device comprise a compound containing at leastthe elements GaAs or InGaAs, or consist of InGaAs or GaAs.

In an example, the stacked III-V semiconductor photonic device includesa further passivation layer, wherein the further passivation layercovers a top side of the III-V semiconductor passivation layer, a sidesurface of the III-V semiconductor passivation layer facing theabsorption region, a top side of the absorption region adjacent to theside surface of the III-V semiconductor passivation layer, and an edgeregion of the top side of the first semiconductor contact region.

Preferably, the further passivation layer comprises Si₃N₄ and/or SiO₂and/or SiNO_(x) and/or polyimide or consists of Si₃N₄ and/or SiO₂ and/orSiNO_(x) and/or polyimide.

In an example, the first semiconductor contact region is produced byimplantation or diffusion of impurity atoms, e.g. Zn or Mg, into theabsorption region. The depth of the first semiconductor contact regionis at least 0.5 μm and at most 20 μm or at most 10 μm or at most 5 μm.The top side of the first semiconductor contact region preferably has acircular or oval or polygonal, e.g. rectangular or octagonal,circumference.

It is understood that the shape of the top side, i.e. the shape of thecircumference, may be produced by a mask used for an implantation step.

In another further development, the stacked III-V semiconductor photonicdevice has a metamorphic buffer layer, wherein the metamorphic bufferlayer is arranged below the bottom side of the absorption region andabove the first metallic terminal contact layer, and has the firstlattice constant on a top side facing the absorption region and a secondlattice constant on a bottom side which differs from the first latticeconstant.

Preferably, the metamorphic buffer layer has a thickness between 2 μmand 5 μm and a doping between 1·10¹⁷ to 1·10¹⁹ cm⁻³. Preferably, themetamorphic buffer layer has at least three semiconductor layers and atmost fifteen semiconductor layers. Preferably, the lattice constants ofthe semiconductor layers of the metamorphic buffer layer change from onesemiconductor layer to the other.

The metamorphic buffer layer is used, for example, to epitaxiallyproduce the absorption region on a substrate which has the secondlattice constant. Alternatively, the buffer layer enables the formationof a semiconductor contact layer from a material which has the secondlattice constant.

In a further development, the III-V semiconductor photonic devicealternatively or additionally comprises a substrate layer, wherein thesubstrate layer is arranged below the bottom side of the absorptionregion and above the first metallic terminal contact layer, and has thefirst lattice constant or a second lattice constant which differs fromthe first lattice constant.

For example, it is possible that a growth substrate on which the layersof the semiconductor device were grown was not completely or onlypartially removed.

In a further development, the stacked III-V semiconductor photonicdevice alternatively or additionally comprises a semiconductorinterlayer having a dopant concentration of 1·10¹⁴-1·10¹⁶ cm⁻³ and alayer thickness of at most 50 μm or at most 20 μm.

The semiconductor interlayer is arranged below the absorption region andabove a highly doped semiconductor contact layer of the secondconductivity type and is of the second conductivity type, or thesemiconductor interlayer is formed between the first semiconductorcontact region and the absorption region and is of the firstconductivity type.

Preferably, the semiconductor interlayer is arranged between the verylow doped absorption region and a highly doped semiconductor contactlayer, i.e., the first semiconductor contact region or a secondsemiconductor contact layer, in order to reduce the series resistance,increase the breakdown resistance, and to achieve better thermalcoupling.

In an example, the absorption region is of the second conductivity typeand the first metallic terminal contact layer is integrally bonded tothe bottom side of the absorption region or to a bottom side of a bufferlayer arranged below the absorption region or to a bottom side of asubstrate layer arranged below the absorption region.

As an alternative to the abovementioned example, the III-V semiconductorphotonic device has a highly doped second semiconductor contact layer ofthe second conductivity type having a dopant concentration of at least1·10¹⁷ cm⁻³, a top side facing the absorption region and a bottom side,wherein the second semiconductor contact layer is arranged below theabsorption region and the first metallic terminal contact layer isintegrally bonded to the bottom side of the second semiconductor contactlayer.

In a further development, the second semiconductor contact layer has alayer thickness of 0.5 μm-150 μm or of 0.5 μm-50 μm or of 0.5 μm and 10μm or of 0.5 μm and 5 μm.

In a further development, the second semiconductor contact layer has thefirst lattice constant and the bottom side of the absorption region ispreferably integrally bonded to the top side of the second semiconductorcontact layer.

In an alternative further development, the semiconductor contact layerhas a second lattice constant which differs from the first latticeconstant, wherein between the semiconductor contact layer and theabsorption region, a buffer layer with the first lattice constant isarranged on a top side facing the absorption region and said bufferlayer with the second lattice constant is arranged on a bottom sidefacing the semiconductor contact layer.

In another embodiment, the semiconductor contact layer is formed as asubstrate layer or as buffer layer. In other words, a singlesemiconductor layer has the function and properties of both thesemiconductor contact layer and the substrate layer or the buffer layeror fulfills both functions.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes, combinations,and modifications within the spirit and scope of the invention willbecome apparent to those skilled in the art from this detaileddescription.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus, are not limitiveof the present invention, and wherein:

FIG. 1 shows a cross-sectional view of a first embodiment of a stackedIII-V semiconductor photonic device,

FIG. 2 shows a plan view of a top side of the first embodiment of thestacked III-V photonic semiconductor device,

FIG. 3 shows a cross-sectional view of a second embodiment of thestacked III-V semiconductor photonic device,

FIG. 4 shows a cross-sectional view of a third embodiment of a stackedIII-V semiconductor photonic device,

FIG. 5 shows a cross-sectional view of a fourth embodiment of a stackedIII-V semiconductor photonic device,

FIG. 6 shows a cross-sectional view of a fifth embodiment of stackedIII-V semiconductor photonic device,

FIG. 7 shows a cross-sectional view of a sixth embodiment of a stackedIII-V semiconductor photonic device,

FIG. 8 shows a plan view of a bottom side of a seventh embodiment of theIII-V semiconductor device, and

FIG. 9 shows a plan view of a bottom side of an eighth embodiment of theIII-V semiconductor device.

DETAILED DESCRIPTION

The illustration of FIG. 1 shows a stacked III-V semiconductor photonicdevice 10 comprising an absorption region 12, a highly doped firstsemiconductor contact region 16, a first metallic terminal contact layer18, a second metallic terminal contact layer 20, and a III-Vsemiconductor passivation layer 22.

The absorption region 12 is doped with dopants of a second conductivitytype having a low to very low dopant concentration of 8·10¹¹-5·10¹⁴ cm⁻³and having a first lattice constant and a layer thickness D12 of atleast 80 μm, e.g., 100 μm or 1000 μm.

On a bottom side of the absorption region 12, the first metallicterminal contact layer 18 follows in a integrally bonded manner as athin planar metallic layer with a thickness D18 of at most 2 μm, e.g. 10nm. Alternatively—not shown—the metallic terminal contact layer 18 isstrip-shaped or finger-shaped or dot-shaped.

The highly doped first semiconductor contact region 16 comprises dopantsof a first conductivity type having a dopant concentration of at least5·10¹⁸ cm⁻³, and extends trough-shaped from the top side of theabsorption region 12 with a width B16 and a depth D16 into theabsorption region 12, so that a top side of the first semiconductorcontact region 16 forms a common surface with the top side of theabsorption region 12.

The second metallic terminal contact layer 20 is arranged on the topside of the first semiconductor contact region 16, wherein the metallicterminal contact layer 20 covers an at least approximatelyconcentrically arranged portion of the top side of the second contactregion 16. The second metallic terminal contact layer 20 is thusarranged in a projection perpendicular to the top side of the absorptionregion, concentric with the second contact region.

At a distance A1 from the top side of the highly doped firstsemiconductor contact region 16, the III-V semiconductor passivationlayer 22 is arranged on the top side of the absorption region 12.

It is understood that the terms “top”, “above”, “bottom” and “below”serve only for the arrangement of the individual regions and layersrelative to each other and do not indicate an absolute direction. Thus,the photonic device shown in FIG. 1 is designed, for example, to detectradiation L coming from below.

The illustration of FIG. 2 shows a plan view of the first embodiment ofthe stacked III-V semiconductor photonic device.

The top side of the first semiconductor contact region 16 has anoctagonal circumference and a diameter B16.

The second metallic terminal contact layer 20 also has an octagonalcircumference and a diameter B20, smaller than the diameter B16, and isconcentrically arranged to the top side of the first semiconductorcontact region 16.

The top side of the first semiconductor contact region 16 is surroundedby an exposed portion of the top side of the absorption region 12,wherein the portion has a width A1 throughout. The remaining surface ortop side of the absorption region 12 is completely covered by the III-Vsemiconductor passivation layer 22, i.e. the III-V semiconductorpassivation layer 22 omits a portion of the absorption region 12 surfacethat comprises the first semiconductor contact region 16.

In embodiments not shown, the circumference of the second metallicterminal contact layer 20, the circumference of the top side of thefirst semiconductor contact region 16 and/or a circumference of therecess in the III-V semiconductor passivation layer 22 are circular,e.g., round or oval, or polygonal, e.g., square or rectangular.

It is understood that said circumferences need not all have the sameshape. The only condition is for the circumference of the secondmetallic terminal contact layer 20 to be at a distance from thecircumference of the top side of the first semiconductor contact region16 at all points and for the circumference of the recess of the III-Vpassivation layer 22 to have at all points at least the first distanceA1 to the circumference of the top side of the first semiconductorcontact region 16.

The illustration of FIG. 3 shows a cross-sectional view of the stackedIII-V semiconductor photonic device in a second embodiment.

A top side of the III-V semiconductor passivation layer 22 is covered byanother passivation layer 24, e.g. a nitride layer and/or an oxide layerand/or a polyimide layer.

The further passivation layer 24 also extends over a portion of the topside of the absorption region, which surrounds the first semiconductorcontact region 16 and is not covered by the first III-V semiconductorpassivation layer 24, and over an edge region of the top side of thefirst semiconductor contact region 16 and a side surface of the III-Vsemiconductor passivation layer 22 oriented toward the firstsemiconductor contact region 16.

The second metallic terminal contact layer 20 covers the exposed centralregion of the top side of the first semiconductor contact region 16 andan adjoining region of the further passivation layer 24.

Between the absorption region 12 and the first metallic terminal contactlayer 18, a second highly doped semiconductor contact layer 14 of thesecond conductivity type having a dopant concentration of at least 10¹⁷cm⁻³ and a layer thickness D14 of at most 20 μm or at most 5 μm or atmost 2 μm or at most 0.5 μm and in any case greater than 10 nm isarranged.

The first metallic terminal contact layer 18 is formed in a integrallybonded manner as a thin planar metallic layer with a layer thickness D18of at most 2 μm, e.g. 10 nm, on a bottom side of the semiconductorcontact layer 14. Alternatively—not shown—the metallic terminal contactlayer 18 is strip-shaped or finger-shaped or dot-shaped.

In the embodiment shown, the absorption region 12 is either of the firstor the second conductivity type, wherein a p-n junction, in the firstcase, forms at the bottom side of the absorption region towards thesecond semiconductor contact layer 14 and, in the second case, forms atthe junction between the absorption region 12 and the trough-shapedfirst semiconductor contact region. The first conductivity type is n andthe second conductivity type is p, or vice versa.

FIG. 4 shows a sectional view of a third embodiment of the stacked III-Vsemiconductor photonic device. In the following, only the differences tothe illustration of FIGS. 1 and 2 are explained.

The stacked III-V semiconductor photonic device 10 has, in addition tothe second semiconductor contact layer 14, a semiconductor interlayer34, wherein the semiconductor interlayer 34 is arranged between thesemiconductor contact layer 14 and the absorption region 12, has a layerthickness of at most 50 μm, is of the second conductivity type and has adopant concentration between 1·10¹⁴ cm⁻³ and 1·10¹⁶ cm⁻³.

FIG. 5 shows a sectional view of a fourth embodiment of the stackedIII-V semiconductor photonic device. In the following, only thedifferences to the illustration of FIGS. 1 and 4 are explained.

The stacked III-V photonic device 10 does not have a highly dopedsemiconductor contact layer 14.

The semiconductor interlayer 34 is arranged between the absorptionregion 12 and the trough-shaped first semiconductor contact region 16and has a layer thickness of at most 20 μm and is of the firstconductivity type.

In an embodiment, not shown, the III-V semiconductor device has both thesecond semiconductor contact layer 14 and the semiconductor interlayerin FIG. 4 and the semiconductor interlayer 34 in FIG. 5 .

FIG. 6 shows a sectional view of a fifth embodiment of the stacked III-Vsemiconductor photonic device. In the following, only the differences tothe illustration of FIG. 1 are explained.

On a top side of the III-V semiconductor passivation layer 22 of theIII-V semiconductor photonic device 10, a third metallic terminalcontact layer 30 formed at least in regions is arranged and integrallybonded to the top side of the III-V semiconductor passivation layer 22.

In addition, the III-V semiconductor passivation layer 22 is of thesecond conductivity type, the absorption region 12 as well as the firstsemiconductor contact region 12 are of the first conductivity type, andthe second semiconductor contact layer 18 is of the second conductivitytype.

FIG. 7 shows a sectional view of a sixth embodiment of the stacked III-Vsemiconductor photonic device. In the following, only the differences tothe illustration of FIG. 1 are explained.

The III-V semiconductor photonic device 10 also has a buffer layer 32,wherein the buffer layer 32 has the first lattice constant on a top sideand a second lattice constant on a bottom side.

The top side of the buffer layer 32 is integrally bonded to the bottomside of the absorption region 12, and the bottom side of the bufferlayer 32 is integrally bonded to the top side of the highly dopedsemiconductor contact layer 14. The semiconductor contact layer 14 hasthe second lattice constant.

In an alternative embodiment, not shown, the III-V semiconductorphotonic device has the buffer layer 32, but no semiconductor contactlayer 14, so that the first metallic terminal contact layer 18 isintegrally bonded to the bottom side of the buffer layer 32.

Also not shown are further developments in which the III-V semiconductorphotonic device 10 has, instead of the buffer layer 32, a substratelayer with the first lattice constant or has, in addition to the bufferlayer 32 and arranged below the buffer layer 32, a substrate layer withthe second lattice constant.

It is understood that the two aforementioned embodiments can be realizedboth with the highly doped semiconductor contact layer and without thesemiconductor contact layer 14.

It is noted that the III-V semiconductor photonic devices in theembodiments of FIGS. 3 to 8 may also have a further passivation layer 24(not shown).

In the illustration of FIGS. 8 and 9 , plan views of a bottom side ofthe III-V semiconductor device are shown in a seventh and eighthembodiment, respectively. In the following, only the differences to theillustration of FIG. 1 are explained.

FIG. 8 shows a finger-shaped embodiment of the first metallic terminalcontact layer 18, wherein the individual finger-shaped sections of thefirst terminal contact layer 18 in the illustrated embodiment runparallel to one another and are electrically conductively connected bymeans of a transversely running finger-shaped section.

FIG. 9 shows a dot-shaped configuration of the first metallic terminalcontact layer 18 on the second semiconductor contact layer 14, whereinthe first terminal contact layer 18 has a square circumference and isarranged in a corner of the bottom side of the absorption region 12.

Not shown are embodiments with a dot-shaped terminal contact layer 18having a rectangular, polygonal, circular or oval circumference with anyposition on the bottom side of the absorption region.

Also not shown are embodiments in which the dot-shaped terminal contactlayer 18 is arranged directly on the absorption region 12 or on anothersemiconductor interlayer 24.

It is also understood that the embodiments of the figures are compatiblewith each other.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are to beincluded within the scope of the following claims.

What is claimed is:
 1. A stacked III-V semiconductor photonic device, comprising: a second metallic terminal contact layer; a highly doped first semiconductor contact region of a first conductivity type having a dopant concentration of at least 5·10¹⁸ cm⁻³ and with a first lattice constant and a first energy band gap; an absorption region of a second conductivity type or of the first conductivity type having a dopant concentration of 8·10¹¹-5·10¹⁴ cm⁻³ and a layer thickness between 80 μm and 2000 μm, wherein the absorption region has the first lattice constant; a first metallic terminal contact layer; and a III-V semiconductor passivation layer with the first lattice constant and a second energy bandgap which differs from the first energy bandgap, wherein the first semiconductor contact region is trough-shaped with a top side and a depth extending into the absorption region, wherein a bottom side of the second metallic terminal contact layer is integrally bonded to the top side of the first semiconductor contact region, wherein the first metallic terminal contact layer is arranged below a bottom side of the absorption region, wherein the III-V semiconductor passivation layer is of the first conductivity type or the second conductivity type and has a dopant concentration in a range between 1·10¹⁴ and 1·10¹⁸ cm⁻³, and wherein the III-V semiconductor passivation layer is arranged on the top side of the absorption region at a first distance of at least 10 μm to the top side of the first semiconductor contact region and is integrally bonded to the top side of the absorption region.
 2. The stacked III-V semiconductor photonic device according to claim 1, wherein the III-V semiconductor passivation layer has a layer thickness of 0.1 μm-10 μm.
 3. The stacked III-V semiconductor photonic device according to claim 1, wherein the III-V semiconductor passivation layer comprises InGaP or AlGaAs or InGaAsP.
 4. The stacked III-V semiconductor photonic device according to claim 1, wherein the first distance of the III-V semiconductor passivation layer to the semiconductor contact region is at least 50% of the layer thickness of the absorption region.
 5. The stacked III-V semiconductor photonic device according to claim 1, wherein the III-V semiconductor passivation layer, in a projection perpendicular to the top side of the semiconductor contact region, completely surrounds the semiconductor contact region.
 6. The stacked III-V semiconductor photonic device according to claim 1, further comprising: a third metallic terminal contact layer bonded to a top side of the semiconductor passivation layer, wherein the absorption region is of the first conductivity type and the III-V semiconductor passivation layer is of the second conductivity type.
 7. The stacked III-V semiconductor photonic device according to claim 1, wherein the III-V semiconductor passivation layer is epitaxially produced on the absorption region and the absorption region is produced on a semiconductor contact layer or on a buffer layer or on a substrate layer.
 8. The stacked III-V semiconductor photonic device according to claim 1, wherein the first metallic terminal contact layer has a layer thickness of 10 nm-1 μm.
 9. The stacked III-V semiconductor photonic device according to claim 1, wherein the first metallic terminal contact layer is flat or finger-shaped or dot-shaped.
 10. The stacked III-V semiconductor photonic device according to claim 1, wherein the first semiconductor contact region and the absorption region and/or a second semiconductor contact layer comprises GaAs.
 11. The stacked III-V semiconductor photonic device according to claim 1, further comprising: a further passivation layer covering a top side of the III-V semiconductor passivation layer, a side surface of the Ill-V semiconductor passivation layer facing the absorption region, a top side of the absorption region adjacent to the side surface of the III-V semiconductor passivation layer, and an edge region of the top side of the first semiconductor contact region.
 12. The stacked III-V semiconductor photonic device according to claim 11, wherein the further passivation layer comprises Si₃N₄ and/or SiO₂ and/or SiNO_(x) and/or polyimide.
 13. The stacked III-V semiconductor photonic device according to claim 1, wherein the first semiconductor contact region is produced by implantation or diffusion of impurity atoms into the absorption region.
 14. The stacked III-V semiconductor photonic device according to claim 1, wherein the depth of the first semiconductor contact region is at least 0.5 μm and at most 20 μm.
 15. The stacked III-V semiconductor photonic device according to claim 1, wherein the top side of the first semiconductor contact region has a circular or an oval or a polygonal circumference.
 16. The stacked III-V semiconductor photonic device according to claim 1, wherein the first conductivity type is n and the second conductivity type is p or wherein the first conductivity type is p and the second conductivity type is n.
 17. The stacked III-V semiconductor photonic device according to claim 1, further comprising: a buffer layer arranged below the bottom side of said absorption region and above the first metallic terminal contact layer, wherein the buffer layer, on a top side facing the absorption region, has the first lattice constant and, on a bottom side, has a second lattice constant which differs from the first lattice constant.
 18. The stacked III-V semiconductor photonic device according to claim 1, further comprising: a substrate layer arranged below the bottom side of the absorption region and above the first metallic terminal contact layer and has the first lattice constant or a second lattice constant which differs from the first lattice constant.
 19. The stacked III-V semiconductor photonic device according to claim 1, further comprising: a semiconductor interlayer having a dopant concentration of 1·10¹⁴ cm⁻³-1·10¹⁶ cm⁻³ and having a layer thickness of at most 50 μm or at most 20 μm, wherein the semiconductor interlayer is arranged below the absorption region and above a highly doped semiconductor contact layer of the second conductivity type and is of the second conductivity type and/or the semiconductor interlayer is formed between the first semiconductor contact region and the absorption region and is of the first conductivity type.
 20. The stacked III-V semiconductor photonic device according to claim 1, further comprising: a highly doped second semiconductor contact layer of the second conductivity type having a dopant concentration of at least 1·10¹⁷ cm⁻³, a top side facing the absorption region and a bottom side, wherein the second semiconductor contact layer is arranged below the absorption region and the first metallic terminal contact layer is integrally bonded to the bottom side of the second semiconductor contact layer.
 21. The stacked III-V semiconductor photonic device according to claim 20, wherein the second semiconductor contact layer has a layer thickness of 0.5 μm-150 μm.
 22. The stacked III-V semiconductor photonic device according to claim 20, wherein the second semiconductor contact layer has the first lattice constant.
 23. The stacked III-V semiconductor photonic device according to claim 21, wherein the bottom side of the absorption region is integrally bonded to the top side of the semiconductor contact layer.
 24. The stacked III-V semiconductor photonic device according to claim 21, wherein the semiconductor contact layer has a second lattice constant which differs from the first lattice constant, and wherein between the semiconductor contact layer and the absorption region a buffer layer is arranged with the first lattice constant at a top side facing the absorption region and with the second lattice constant at a bottom side facing the semiconductor contact layer.
 25. The stacked III-V semiconductor photonic device according to claim 20, wherein the semiconductor contact layer is formed as a substrate layer or a buffer layer. 